The game borrows from Zelda II: The Adventure of Link and implements its mechanics haphazardly. The experience system is taken from Zelda II, which was released nearly a year earlier in Japan.
The password system is quite convoluted due to the font used in this game. Some lowercase letters can be mistaken for uppercase letters or numbers.
The screen repeatedly flashes red when your HP is low. There's no way to disable this.
Your default weapon, the knife, has pathetic range. It tries to copy the Sword from Zelda II but with even shorter range.
While you can get better weapons, they have limited ammunition.
The graphics and sprites are sub-par for its time. Rambo's side-scrolling sprite barely resembles his likeliness.
It can get too difficult for its own good at times. A good example is when you get to the base, where special forces take a lot of hits before they go down.
The controls don't seem to be responsive at times.
You can easily get lost wandering in the jungles of Vietnam. Due to some screens looking similar to one another, you can imagine how frustrating it was to spend hours going in an endless loop and not understand why.
Poor hitboxes. Your knife sometimes can stab an enemy and it doesn't register as a hit.
The final boss fight against the chopper is impossible if you don't have the right weapons for it.
The music is at least good.
It follows the plot of First Blood Part II faithfully, for the most part.
The American version fixes Rambo's hair color from talking sense. (while the Japanese version of Rambo's hair is green)